Manual bone cement mixing system with vacuum pump start-stop device

Abstract

A system for mixing bone cement is disclosed. Dry PMMA powder and MMA liquid are mixed in a vacuum chamber. Gas from the mixture is vacuum drawn from the mixer by a vacuum source through a vacuum tube which extends between the mixer and the vacuum source. The vacuum source is actuated by creating a positive pressure pulse in the vacuum tube. The pressure pulse may be caused by closing the lid of the mixer, by squeezing an in-line pressure bulb in the vacuum tube or by squeezing a pressure bulb joined to the vacuum tube. The vacuum source is automatically deactivated when a positive vacuum pulse is detected. The second pressure pulse is caused when the vacuum tube is disconnected from the vacuum chamber.

What I claim as my invention is: 
     
       1. A system for mixing bone cement comprising, a) a device for mixing bone cement having a hollow mixing chamber and a vacuum port;   b) a vacuum tube having a first end attached to said port and a second end; and   c) a vacuum source including a vacuum pump having an inlet port connected to the second end of the vacuum tube, and a vacuum pump start and stop device operatively joined to the pump to start the pump in response to a positive pressure pulse above ambient and to automatically stop the pump in response to a positive pressure pulse above a vacuum.   
     
     
       2. A system as in claim 1 including an electric motor for the pump, a power line for the motor and wherein the vacuum pump start and stop device includes an electronic pressure transducer connected to the inlet port, a power switch connected in the power line for the motor and a circuit element operable to actuate the switch when the transducer senses a positive pressure pulse at the inlet port. 
     
     
       3. A system as in claim 2 including a piston lid for the hollow mixing chamber whereby closing the lid onto the chamber causes an increase in pressure. 
     
     
       4. A system as in claim 2 including a pressure bulb connected to the vacuum tube whereby squeezing the bulb causes an increase in pressure. 
     
     
       5. A system as in claim 4 including a check valve between the bulb and the mixing chamber. 
     
     
       6. A system as in claim 2 including a second tube joining the vacuum tube and a pressure bulb on the end of the second tube. 
     
     
       7. A system for mixing bone cement including a bone cement mixing chamber, a vacuum source, a first tube joining the vacuum source to the interior of the mixing chamber so that the source reduces the pressure within the chamber, a pressure pulse generator connected to either the mixing chamber or the first tube, and a sensing circuit operably connected to the vacuum source to actuate the vacuum source in response to a pressure pulse from said pulse generator. 
     
     
       8. A system as in claim 7 wherein said pulse generator compresses a squeeze bulb connected to said tube. 
     
     
       9. The device of claim 7 wherein said pulse generator includes a piston lid for the mixing chamber. 
     
     
       10. The device of claim 7 wherein said pulse generator includes a bulb joined to the vacuum tube whereby squeezing the bulb causes a pressure pulse to activate the vacuum source. 
     
     
       11. A device as in claim 10 including a check valve located between the bulb and the chamber. 
     
     
       12. The device of claim 7 wherein said pulse generator includes a squeeze bulb and a second tube extending between the first tube and the bulb. 
     
     
       13. A device as in claim 12 including a check valve in the first tube adjacent the mixing chamber.